Preparation of an oxide-free halide of a rare refractory metal



! e23-253 1 se i FIP8307 as UNITED STATES PATENT OFFICE JOHN WESLEYMARDEN AND HARVEY CLAYTON RENTSCHLER, OF EAST ORANGE, NEW

JERSEY, ASSIGNORS TO WESTINGHOUSE LAMP COMPANY, A CORPORATION OF PENN-SYLVANIA.

PREPARATION OF AN OXIDE-FREE HALIDE OF A RARE REFRACTORY METAL NoDrawing. Original application fi1ed March 17, 1924, Serial No. 699,942.Divided and this application filed February 16, 1927. Serial No.168,826.

This application is a division of application Serial No. 699,942, filedMarch 17, 1924, assigned to the same assignee as the presentapplication.

This invention relates to the preparation of rare refractory metalcompounds and more particularly to a process for producing an oxide-freehalide of such metals.

One of the objects of our invention is to $0 providea process forpreparing an oxidefree halide salt of a refractory metal.

Another object of our inventionis to provide a process for preparingsalts of the refractory metals which are free from water ofcrystallization.

In the U. S. patent to Marden 1,437,984, granted December 5, 1922, amethod is disclosed for the production of the rare metals in the powderor coherent form by reducing a halide of the metal by means of aluminumor iron under suitable conditions.

The invention described in the aforesaid application is, in a sense, amodification of the process described in the aforesaid patent and isespecially suitable for the production of fused uranium which, as iswell known by scientists, is very difiicult to obtain in such conditionand free from any contaminations which deleteriously affect theproperties of the metal such as its electro-conductivity and the like.

In the preparation of fused rare metals, for example, the inventiondescribed in the parent application first contemplates the production ofa pure oxide-free halide salt of the metal and to secure this end wehave devised a special chemical process which may be employed, althoughit is obvious that other methods might be suitably modified to ob tainthe salt in the condition stated, and, secondly, we have employed as areducing agent a substance which volatilizes readily so that the raremetal may be freed Without difficulty therefrom. The reducing substancepreferably employed by us, is one which may be obtained in substantially100% purity. The present invention relates only to the first stepmentioned.

The oxide-free uranium salt may be prepared by the following processwhich is given for illustrative purposes only.

Two hundred grams of uranyl acetate may be dissolved in distilled waterand filtered into a suitable receptacle such as a wooden or rubber pail.To this solution may be added a solution obtained by dissolving 200grams of potassium fluoride, or, if desired, sodium flouride, and thislatter solution may then be filtered to remove impurities, such asshavings and the like, and the two clear filtered solutions thoroughlymixed together. To this mixture of uranyl and potassium or sodiumfluoride, there may be added 60 cubic centimeters of hydro-fluoric acidand approximately 60 cubic centimeters of formic acid or any othersuitable reducing agent for producing slow crystallization of the salt.N o

The precipitate may be removed from the solution by filtering andthereafter thoroughly washed with distilled water to remove the solubleproducts mixed with the precipitate and the precipitate is then dried byheating in an oven.

After the precipitate has been thoroughly dried, the water ofcrystallization may be removed therefrom by fusing. The fusing operationmay be accomplished by adding to the potassium-uranium fluoride, i. e.,the precipitate, an equal weight of a mixture of equal parts of sodiumand potassium chlorides. It is preferable to employ a mixture of sodiumand potassium chloride in preference to either of these chlorides alone,for the reason such a mixture melts at a lower temperature and is easierto handle.

The fusion may be accomplished by heating a platinum crucible containingthe materials in air over an open flame, in an electric furnace, or inan inert environment, such as hydrogen. The sodium and potassiumchlorides may be placed in a crucible of platinum or other suitablematerial and the potassiumuranium fluoride added, alittle at a time,

I until the fusion is perfectly clear. When this condition has beenreached, it is an indication of the complete fusion of the mixture andthereafter the crucible may be covered and the mass allowed to cool.

The fused mass may be removed from the crucible after cooling and groundto pass a 200 mesh sieve, after which it may be suspended in distilledwater and washed thoroughly to remove all of the excess of sodium andpotassium salts. The residue may be then filtered, washed with alcoholand thereafter dried for approximately one hour at 150 C. in a dryingoven. This salt which is a potassium uranium fluoride which issubsequently used in the process, will be found to be free from oxides.

Heretofore, in the preparation of uranium salts, considerable difficultywas experienced in obtaining a precipitate of uranium fluoride whichcould be filtered and washed, owing to the fact that the precipitate wasso finely divided and so very gelatinous, that it would clog the poresof the filter and thus prevent the separation of the precipitate fromthe solution.

Furthermore, owing to the water present. the latter would decompose andreact with the metal to form oxides. By means of our process, thesedifficulties have been overcome and we are able to secure a courseuranium fluoride which may be filtered very readily and which mayafterwards be fused and obtained in the oxide-free condition.

Modifications of the foregoing process may suggest themselves to thoseskilled in the art, but it is to be appreciated that such modificationsare contemplated by us as fall within the scope of the appended claims.

lVhat is claimed is:

1. The method of removing water of crystallization from uranium doublealkali metal fluorides which comprises fusing said compound with analkali metal halide flux substantially non-reactive therewith andsubstantially free from oxygen containing compounds.

2. The method of dehydrating uraniumpotassium fluoride (KUF plus waterof crystallization) which comprises fusing said compound with a fluxcomprised of equal parts sodium and potassium chlorides.

The method of forming an anhydrous oxide-free double uranium alkalimetal fluoride which comprises initially forming a crystalline doublefluoride compound by precipitation from aqueous solution and thereafterfusing said crystalline compound with a flux comprised substantially ofequal parts sodium and potassium chlorides.

4. The method of forming an anhydrous eXide-free double uranium alkalimetal fluoride which comprises initially forming a crystalline doublefluoride compound containing water of crystallization by precipitationfrom aqueous solution and thereafter fusing said crystalline compoundwith alkali metal chlorides to remove the water of crystallizationtherefrom, said fusion operation being performed with the exclusion ofair and oxygen containing compounds.

In testimony whereof, we have hereunto subscribed our names this 15thday of February, 1927.

JOHN WESLEY MARDEN. HARVEY CLAYTON RENTSCHLER.

